bcrump's blog

Yesterday evening we received waypoints/waytimes from Grant Law for today Feature Tracking Exercise. We did one of these on the 16th during the Spring Tide. Now that it is Neap Tide we are doing it again. We were not able to get to the first way-point in time after pulling the drifter at 08:30, so we started our series a little late. Grant updated the surface salinity forecast for the locations and times we did CTD casts, and the numbers improved.

We pulled the drifter out of the water at 06:30 and motored back to the mouth of the Columbia to do it all again. At 08:00 we deployed a drifter off the stern - the same as yesterday - but it was immediately swept under the ship and broken by the ship's bow thruster. The lesson here is to face the ship into the current when deploying off the stern. So we turned the ship around and deployed the other drifter at 08:30 and set about following it for the next 24 hours. This time the drifter moved northwest and later began to curl back to the northeast.

Today we began a new field campaign for the CMOP program. At the beginning of the strong ebb tide we released an Argos surface drifter at the mouth of the estuary on the south side of the shipping channel. We immediately cast the CTD and collected a surface water sample. Then we followed the drifter as it moved off shore, casting the CTD each hour and collecting a surface water sample every three hours.

Today we attempted to follow an intermediate bottom salinity as it moved up estuary on the flood and down estuary on the ebb. We waited until the strong ebb settled down at about 10:00 pdt and moved to station NC-7, which lies 7 miles up estuary from the mouth. We established a set of stations at half-mile increments from NC-7 to NC-11 near the bridge, including 3 stations spanning the channel at each point. We then worked our way up the estuary with the flood casting the CTD at several of these stations.

Today we set out to collect water samples with no particles at a range of salinities in the North Channel of the Estuary. We did the same thing in the South Channel on July 19th. At the same time the R/V Barnes was positioned in the ETM region of the North Channel collecting ETM samples. We spent most of the day moving between stations NC-7, 9, and 11. Most water samples were collected at a middle depth above the influence of ETM particles. We collected water at the following salinities: 2, 6.5, 10, 18, 26, and 31.

Overnight last night we anchored in the North Channel near the Saturn 01 station and cast the CTD hourly until the morning. We then moved to the south channel to begin a day of CTD casts with the goal of following a specific salinity bottom water (~15), up and down the estuary. We were guided by Joseph Zhang at OHSU who provided way points and times. For most of our casts the surface water was saltier than predicted, and the bottom water was fresher than predicted, suggesting that the forecast model is not capturing the degree of water column mixing.

We left the dock this morning at 5:30 am and headed down estuary to our first sampling station. Our goal today was to collect water samples at a range of salinities and make sure those samples do not have a lot of particles in them. This estuary has very strong Estuarine Turbidity Maxima (ETM) in its north and south channels. ETM are hydrodynamic phenomena in which river-borne particles are trapped and concentrated in the estuary as the freshwater moves through. These particles are resuspended by the tides and settle back to the bed during slack tides.

This morning we docked at the Port of Astoria to switch out some scientific crew members and to pick up our Argos drifters. Our coring team of Mouzhong Xu, Mindy Ingebretson and Paul Walczak got off the ship and were replaced with grad student Caroline Fortunato, undergraduate intern Lauren Vice, and webmaster/videographer Jeff Schilling. We made a run to Fred Meyer for some more buckets and some dry ice for transporting sediment core samples back to OHSU. We also relaxed a little. Many folks went bowling in Astoria.

After we finished sampling the La Push line we spent the night steaming back to the mouth of the Columbia to start a Feature Tracking exercise in the 'young' plume. Grant Law from the modeling team provided a list of way points/times designed to sample across a range of surface salinities within the plume, including a point just outside the plume front. This is a challenge because the plume is very dynamic and changes shape and size dramatically with the tides (see attached movies).

After completing our work on the Cape Falcon line, we spent the nighttime cruising up the Washington, casting the CTD at station along the 100m isobath all the way to LP-12 on the La Push line. We then moved inshore to LP-4 to start the La Push line. We casted the CTD at 10 stations going east to west (LP-4, 6, 9, 12, 17, 22, 27, 32, 42, 52), collected water samples at three depths at four stations (LP-6, 17, 32, 52), measured primary production at one station (LP-6), and collected sediment cores at two stations (LP-17, 52). Our team is now processing samples with confidence and ease.